During gameplay (not in menus), press and hold:
Use this right before a boss fight in Metal Slug 3 . Because the PSP reads the UMD (or memory stick) slowly, loading a state is actually faster than watching the "Continue" countdown. Metal Slug Anthology Psp Cheats
At the title screen (where Marco appears), press: Up, Up, Down, Down, Left, Right, Left, Right, Circle, Cross During gameplay (not in menus), press and hold:
Play or 5 on Hard difficulty (you can use infinite credits). Most extra content is tied to completing the
Most extra content is tied to completing the games under specific conditions: Unlockable Requirement Clear all 7 games on Easy with Limited Continues. Desktops 1 (Wallpapers) Clear all 7 games on Normal with Limited Continues. Desktops 2 & Special Music Clear all 7 games on Hard with Limited Continues. Metal Slug 6 Extras